Butler and Schaller — Minerals from Beaver Co., Utah. 423 



crystals are uniaxial, optically negative with strong birefring- 

 ence. It may be noted that jarosite from the same mines is so 

 similar to the plumbojarosite in physical properties that a dis- 

 tinction can be made onty by chemical tests. 



Chemical composition.— The analysis (by W. T. S.) of the 

 plumbojarosite is shown in the table below, where, for com- 

 parison, are also given the two analyses, by Hillebrand, of the 

 mineral from New Mexico and American Fork, Utah. The 

 values calculated from the formula Pb0.3Fe 2 3 .4S0 3 .6H 2 

 are also given in the last column for comparison. 



Analyses of plumbojarosite. 





Beaver Co., 



Cook's Peak, 



American Fork, 







Utah 



N. M. 



Utah 



Calculated 



Fe 3 3 



42-11 



42'37 



42-87 



42-38 



PbO 



18*32 



19-84 



18-46 



19-74 



K,0 



Na a O 



j-0-13 



0-17 

 0-21 



0-15 

 0-52 







so 3 .__ 



27-59 



27-06 



27-67 



28-33 



H,0 



9-16 



9-56 



10-14 



9-55 



CuO 



- _ - - 



0-27 



o-io 



- - - - 



CaO 



o-oo 



0-05 



006 



- - - - 



Insol 



2-64 



0-51 



0-40 







ZnO 



0-30 

















100-25 



100-15 



100-37 



100-00 



Density 



3-60 



3-665 







The three analyses show a close agreement among themselves 

 as well as with the calculated values. 



Corkite. 



A light yellowish-green mineral that has the properties of 

 corkite, a hydrous phosphate and sulphate of lead and iron, was 

 collected from the Harrington-Hickory and the Wild Bull 

 mines. So far as is known to the writers, these are the only 

 localities on this continent from which this mineral has been 

 reported. 



In both of the mines mentioned the original ores were 

 a replacement of limestone near the intrusive rock and there 

 was considerable apatite and contact silicates formed with the 

 metallic sulphides, mainly pyrite, galena, sphalerite, and chal- 

 copyrite. The corkite is a secondary mineral resulting from 

 the alteration of these ores, the phosphate doubtless being 

 derived from the apatite and the metallic content from the 

 sulphides. 



